<button>Hover over me</button>
<style>
button{
	background-color:hsl(180,50%,50%);
	border:0;
	color:white;
	font-size:1rem;
	padding:.3em 1em;
	transition-property:all;
	transition-duration:0.5s;
}
button:hover{
	background-color:hsl(0,50%,50%);
	border-radius:1em;
}
</style>